| FDEG | int | Degrees of freedom of Chebychev polynomials | | |
| NITER | int | The number of iterations during solving | | |
| PDEG | int | Degrees of freedom for plate polynomials | | |
| THRESHFRAC | float | The fraction of the maximum threshold below which the iteration is allowed to threshold | | |
| VERBOSE | str | Verbosity level (NONE, NORMAL, VERBOSE, DEBUG) | | |
| XMAX | float | Maximum X-coordinate of useful pixel plane | | |
| XMIN | float | Minimum X-coordinate of useful pixel plane | | |
| XPIXSIZE | float | The scaling of pixels with which CDELT1 is multiplied | | |
| YMAX | float | Maximum Y-coordinate of useful pixel plane | | |
| YMIN | float | Minimum Y-coordinate of useful pixel plane | | |
| YPIXSIZE | float | The scaling of pixels with which CDELT2 is multiplied | | |
